One process useful in the continuous scaling down of features is an atomic layer etch during plasma processing of a substrate. Conventionally, the atomic layer etch is performed using a processing scheme which relies on switching gas mixtures to achieve the appropriate plasma chemical composition for passivation (functionalization, adsorption, deposition) and the appropriate plasma chemical composition for a subsequent etch process.
Typically, the substrate is first exposed to a minimally etching plasma to passivate an upper layer. During the passivation process, the ion energies of the plasma should be less than the threshold for etching the passivated top layer. Next, the passivated layer is exposed to an etching plasma to remove the passivated top layer. During the etch process, the ion energies of the plasma should be less than the threshold for sputtering the unpassivated substrate. However, such a scheme suffers from slow processing speeds due to the purging of the process chamber of the previous gas mixture between the passivation and etching processes. Accordingly, the inventor has provided an improved method of processing a substrate that achieves atomic layer etching at significantly higher speeds.
Accordingly, the inventor has developed improved methods of processing a substrate.